The present invention relates to a nonaqueous electrolyte battery in which a battery element is contained in an outer covering member composed of a laminated film.
In recent years, along with strong demands toward reductions in size and weight in the field of portable electronic equipment such as a camera integrated VTR, a cellular phone, and a portable computer, batteries used as portable power sources of the portable electronic equipment have been also required to be reduced in size and weight. To meet such a requirement, studies have been extensively made to develop thin type or foldable type batteries, particularly, secondary batteries, more particularly, nonaqueous electrolyte batteries (so-called lithium batteries).
As an electrolyte used for the above-described foldable battery, a solid electrolyte has been actively made. In particular, a gel electrolyte composed of a solid electrolyte containing a plasticizer and a high polymer solid electrolyte including a lithium salt dissolved in a high polymer have become a focus of attention.
On the other hand, to attain the reductions in size and weight of batteries, studies have been also made to develop batteries of a type including a battery element enclosed in a plastic film or a so-called laminated film obtained by laminating a metal film to a plastic film.
The so-called laminated film, however, has a problem. For a conventional battery using a metal container, the metal container having a high rigidity is little deformed even if a pressure in the battery is raised. On the contrary, for a battery using the laminated film, if the battery is erroneously charged or discharged due to a failure of a control circuit or the like or is left under an abnormal high-temperature environment, then the laminated film having a low rigidity is possibly swelled by an increase in pressure in the battery due to gas occurred by the abnormal reaction of constituent materials of the battery.